clk: samsung: add Exynos ACPM clock driver

Add the Exynos ACPM clock driver. It provides support for clocks that
are controlled by firmware that implements the ACPM interface.

Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Tested-by: Peter Griffin <peter.griffin@linaro.org> # on gs101-oriole
Link: https://patch.msgid.link/20251010-acpm-clk-v6-4-321ee8826fd4@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

drivers/clk/samsung/Kconfig

@@ -95,6 +95,16 @@ config EXYNOS_CLKOUT
 	  status of the certains clocks from SoC, but it could also be tied to
 	  other devices as an input clock.
 
+config EXYNOS_ACPM_CLK
+	tristate "Clock driver controlled via ACPM interface"
+	depends on EXYNOS_ACPM_PROTOCOL || (COMPILE_TEST && !EXYNOS_ACPM_PROTOCOL)
+	help
+	  This driver provides support for clocks that are controlled by
+	  firmware that implements the ACPM interface.
+
+	  This driver uses the ACPM interface to interact with the firmware
+	  providing all the clock controlls.
+
 config TESLA_FSD_COMMON_CLK
 	bool "Tesla FSD clock controller support" if COMPILE_TEST
 	depends on COMMON_CLK_SAMSUNG

drivers/clk/samsung/Makefile

@@ -28,6 +28,7 @@ obj-$(CONFIG_EXYNOS_ARM64_COMMON_CLK)	+= clk-exynos990.o
 obj-$(CONFIG_EXYNOS_ARM64_COMMON_CLK)	+= clk-exynosautov9.o
 obj-$(CONFIG_EXYNOS_ARM64_COMMON_CLK)	+= clk-exynosautov920.o
 obj-$(CONFIG_EXYNOS_ARM64_COMMON_CLK)	+= clk-gs101.o
+obj-$(CONFIG_EXYNOS_ACPM_CLK)		+= clk-acpm.o
 obj-$(CONFIG_S3C64XX_COMMON_CLK)	+= clk-s3c64xx.o
 obj-$(CONFIG_S5PV210_COMMON_CLK)	+= clk-s5pv210.o clk-s5pv210-audss.o
 obj-$(CONFIG_TESLA_FSD_COMMON_CLK)	+= clk-fsd.o

drivers/clk/samsung/clk-acpm.c

@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Samsung Exynos ACPM protocol based clock driver.
+ *
+ * Copyright 2025 Linaro Ltd.
+ */
+
+#include <linux/array_size.h>
+#include <linux/clk-provider.h>
+#include <linux/container_of.h>
+#include <linux/device/devres.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/firmware/samsung/exynos-acpm-protocol.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+struct acpm_clk {
+	u32 id;
+	struct clk_hw hw;
+	unsigned int mbox_chan_id;
+	const struct acpm_handle *handle;
+};
+
+struct acpm_clk_variant {
+	const char *name;
+};
+
+struct acpm_clk_driver_data {
+	const struct acpm_clk_variant *clks;
+	unsigned int nr_clks;
+	unsigned int mbox_chan_id;
+};
+
+#define to_acpm_clk(clk) container_of(clk, struct acpm_clk, hw)
+
+#define ACPM_CLK(cname)					\
+	{						\
+		.name		= cname,		\
+	}
+
+static const struct acpm_clk_variant gs101_acpm_clks[] = {
+	ACPM_CLK("mif"),
+	ACPM_CLK("int"),
+	ACPM_CLK("cpucl0"),
+	ACPM_CLK("cpucl1"),
+	ACPM_CLK("cpucl2"),
+	ACPM_CLK("g3d"),
+	ACPM_CLK("g3dl2"),
+	ACPM_CLK("tpu"),
+	ACPM_CLK("intcam"),
+	ACPM_CLK("tnr"),
+	ACPM_CLK("cam"),
+	ACPM_CLK("mfc"),
+	ACPM_CLK("disp"),
+	ACPM_CLK("bo"),
+};
+
+static const struct acpm_clk_driver_data acpm_clk_gs101 = {
+	.clks = gs101_acpm_clks,
+	.nr_clks = ARRAY_SIZE(gs101_acpm_clks),
+	.mbox_chan_id = 0,
+};
+
+static unsigned long acpm_clk_recalc_rate(struct clk_hw *hw,
+					  unsigned long parent_rate)
+{
+	struct acpm_clk *clk = to_acpm_clk(hw);
+
+	return clk->handle->ops.dvfs_ops.get_rate(clk->handle,
+					clk->mbox_chan_id, clk->id);
+}
+
+static int acpm_clk_determine_rate(struct clk_hw *hw,
+				   struct clk_rate_request *req)
+{
+	/*
+	 * We can't figure out what rate it will be, so just return the
+	 * rate back to the caller. acpm_clk_recalc_rate() will be called
+	 * after the rate is set and we'll know what rate the clock is
+	 * running at then.
+	 */
+	return 0;
+}
+
+static int acpm_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+			     unsigned long parent_rate)
+{
+	struct acpm_clk *clk = to_acpm_clk(hw);
+
+	return clk->handle->ops.dvfs_ops.set_rate(clk->handle,
+					clk->mbox_chan_id, clk->id, rate);
+}
+
+static const struct clk_ops acpm_clk_ops = {
+	.recalc_rate = acpm_clk_recalc_rate,
+	.determine_rate = acpm_clk_determine_rate,
+	.set_rate = acpm_clk_set_rate,
+};
+
+static int acpm_clk_register(struct device *dev, struct acpm_clk *aclk,
+			     const char *name)
+{
+	struct clk_init_data init = {};
+
+	init.name = name;
+	init.ops = &acpm_clk_ops;
+	aclk->hw.init = &init;
+
+	return devm_clk_hw_register(dev, &aclk->hw);
+}
+
+static int acpm_clk_probe(struct platform_device *pdev)
+{
+	const struct acpm_handle *acpm_handle;
+	struct clk_hw_onecell_data *clk_data;
+	struct clk_hw **hws;
+	struct device *dev = &pdev->dev;
+	struct acpm_clk *aclks;
+	unsigned int mbox_chan_id;
+	int i, err, count;
+
+	acpm_handle = devm_acpm_get_by_node(dev, dev->parent->of_node);
+	if (IS_ERR(acpm_handle))
+		return dev_err_probe(dev, PTR_ERR(acpm_handle),
+				     "Failed to get acpm handle\n");
+
+	count = acpm_clk_gs101.nr_clks;
+	mbox_chan_id = acpm_clk_gs101.mbox_chan_id;
+
+	clk_data = devm_kzalloc(dev, struct_size(clk_data, hws, count),
+				GFP_KERNEL);
+	if (!clk_data)
+		return -ENOMEM;
+
+	clk_data->num = count;
+	hws = clk_data->hws;
+
+	aclks = devm_kcalloc(dev, count, sizeof(*aclks), GFP_KERNEL);
+	if (!aclks)
+		return -ENOMEM;
+
+	for (i = 0; i < count; i++) {
+		struct acpm_clk *aclk = &aclks[i];
+
+		/*
+		 * The code assumes the clock IDs start from zero,
+		 * are sequential and do not have gaps.
+		 */
+		aclk->id = i;
+		aclk->handle = acpm_handle;
+		aclk->mbox_chan_id = mbox_chan_id;
+
+		hws[i] = &aclk->hw;
+
+		err = acpm_clk_register(dev, aclk,
+					acpm_clk_gs101.clks[i].name);
+		if (err)
+			return dev_err_probe(dev, err,
+					     "Failed to register clock\n");
+	}
+
+	return devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get,
+					   clk_data);
+}
+
+static const struct platform_device_id acpm_clk_id[] = {
+	{ "gs101-acpm-clk" },
+	{}
+};
+MODULE_DEVICE_TABLE(platform, acpm_clk_id);
+
+static struct platform_driver acpm_clk_driver = {
+	.driver	= {
+		.name = "acpm-clocks",
+	},
+	.probe = acpm_clk_probe,
+	.id_table = acpm_clk_id,
+};
+module_platform_driver(acpm_clk_driver);
+
+MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@linaro.org>");
+MODULE_DESCRIPTION("Samsung Exynos ACPM clock driver");
+MODULE_LICENSE("GPL");